Các câu hỏi tương tự
s=1x2+2x3+3x4+.........+2020x2021
1x2+2x3+3x4+...+1999x2000
tính tổng
1x2+2x3+3x4+...+19x20
1x2+2x3+3x4+...+98x99+99x100 = ?
1x2+2x3+3x4+...+(nxn+1)
1x2+2x3+3x4+...+(nxn+1)
Tinh : 1x2+2x3+3x4+...+99x100
A= 1x2+ 2x3+ 3x4+ ....+18x20
1X2+2X3+3X4+..........+99X100+100X101